Manufacture of whiting



v 1,634,877 y P. M. MCHUGH MANUFACTURED! WHITING Filed March 13, 1,924

YIll!IIIIIIIIIIII"Illlllllllllllllllllll Phih a M. M I- ugh INVENTOR TTO NEY Patented July 5, 1927.

UNITED STATES PATENT OFFICE.

PHILIP H. EOHUGH, OF IPELHAM MANOR, NEW YORK, ASSIGN'OR TO THE DORR COM- rm, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

' mannrac'rnnn or WHITING.

Application filed Harch 18, 1924, Serial No. 698,843, and in Germany March 14, 1923'.

This invention relates to improvements in the manufacture of whiting, and is particularly directed to the treatment of ground chalk to eliminate grit therefrom and produce a grit-free whiting of the requisite fineness. In view of the extremely small mesh size of the whiting, and the fact that the grit is also very fine, the removal of the latter presents a definite and unusual problem in accurate classification of fine particles.

According? the known method for manufacturing w 'ting, the limestone suspension obtained from the wet grinding of chalk is refined in overflow apparatus, and settled in settling troughs which are emptied from time to time. The process is discontinuous and for this reason uneconomic. Furthermore, the point of discharge of the pulp from the flume varies as the trough fills, and it is in practice impossible to make an efficient separation owing to the impossibility of adjusting constantly the point of withdrawal from the trough. Dry griding was also proposed for carrying out this process continuously, and it was proposed to draw off by means of suction the fine product suitable for the manufacture of whitewash or whiting. it has turned out, however, that by this method a product is produced whose quality varies considerably, and therefore, is commercially unsuitable; and indeed nothing else was to be expected from the notoriously irregular operation of suction.

The invention submitted is designed to eliminate this disadvantage. For this purpose, the suspension obtamed from the wet grinding is led to an overflow-separator (hydroseparator) from the bottom of which a sand rich in fine material is drawn, and this sand is conveyed to a classifying apparatus to recover the fines, from whence the fines are passed back into the hydroseparator.

As a classifying apparatus, for the above described pur ose, the known Dorr classifier according to erman Patent No. 287,463, and the mode of operation shown in this patent, is especially suited The same machine is shown in United States Patent No. 1,292,237

and comprises a combination of a settling usually fine mesh, with a minimum of undersize in the sand or grit discharged from the rakes.

A tank-equipped with rotating stirring paddles is suitable for use as a hydrosepa rator, whereby the raking paddles propel the sand which has collected on the bottom toward a central discharge opening. ,For forwarding the discharged sand into the classifying apparatus, any sort of conveying device, pumps, etc. may be used. The overflow from the hydroseparator, carr ing suspended solids, is suitably settle in the known Dorr thickener, and discharged.

The hydroseparator is in addition so adjusted that it furnishes a sand product rich in fines, so that absolute surety is given that no sandy product gets into the overflow. Thus a completely sand free, and in every respect uniform whitewash or whiting product is continuously produced. It will be recognized by those familiar with this type of machine that the hydroseparator is adapted to handle large flows, but is ineflicient in recovering a sufficiently large proportion of the fine material; while the Bowl classifier,

V tho particularly eflicient'in recovery of fines,

would have to be built in exceptionally large sizes to handle large flows.

By dividing of the work between two machines these do not need to be nearly so large as if only one were used, so that the material and plant costs need not be greater than if a single, correspondingly larger apparatus were used.

These machines, as is well known, are both continuous in operation, and are thereby distinguished from the prior practice in which troughs had to be shut down and cleaned out periodically. This arrangement is therefore particularly advantageous; as continuous apparatus can readily be provided before and after the units herein described. Furthermore, if desired the bowl overflow can be returned to the hydroseparator, which means that the Bowl classifier may be overloaded to a certain extent without sacrificing the finer product, an arrangement that is particularly economical commercially.

One plan for carrying out the process is schematically shown. by way of example, in the attached drawing. The suspension com-' ing from the wet grinding is led through the feed conduit- (z of the hydroseparator b, in which rotates a stirring apparatus h, equipped with rakes. The overflow, containing only fines, goes through the passage 0 to suitable settling apparatus. The recovered sand rich in fines is pushed by the rakes toward a centrally located discharge opening on the bottom of the tank 7), and from there is carried by means of the pump (i, into a classifying apparatus 0 of the type disclosed in German Patent 287,463, and in the United States Patent No. 1,292,237. Here the fines are separated out, and by means of passage f are led back into the hydroseparator. The sand is removed and discharged by the classifier rakes i.

It is noted that the novelty in the invention does not involve the arrangement of the apparatus but only the method of working thereof in cooperation for producing a sandfree and entirely uniform product for the manufacture of whitewash, whiting or the like.

I claim:

1. A method for the classification of fine solids suspended in liquid which comprises the removal of a portion of the undersize hydraulically; removing the remaining solids which comprise the oversize and the residue of the undeisize, subjecting such remainder to a classifying step for separating said residue from the oversize, and returning the separated residue to the hydraulic removal step independently of thefeed to the classifying step.

2. A method for the classification of fine solids suspended in liquid which comprises the removal of a portion of the undersize solids by hydroseparation; removing the remaining solids which comprise the oversize and the residue of the undersize, as an underflow from the hvdroseparation step; subjecting the remainder to a classifying step for separating said residue from the oversize, and returning the separated residue to the hydroseparation step independently of the feed to the classifying step.

3. A method for the continuous classification of fine solids suspended in liquid which comprises the continuous removal of a portion of the undersize solids hydraulically, the continuous removal of the remainder of the solids which com rises the oversize and the residue of the undersize, subjecting such remainder to a classifying step for separating such residue from the oversize, and continuously returning the separated residue to the hydraulic separating step independently of the feed to the classifying step.

43A method for the classification of fine solids suspended in liquids which comprises the removal of a portion of the undersize solids by hydroseparation, removal of the remaining solids which comprise the oversize and the residue of the undersize, through a passage exclusively occupied by said remaining solids and liquid therewith flowing away from the hydroscparation step; subjecting said remaining solids to a classifying step for separating said residue from the oversize, and returning the separated residue to the hydroseparation step.

5. A method for the classification of fine solids suspended in liquid which comprises removing a portion of the undersize solids by hydroseparation; impelling the settled solids, comprising the oversize solids and the residue of the undersize, toward a discharge; conveying the settled solids through a discharge passage occu ied exclusively by said solids with liquid owing away from the hydroscparation step, subjecting the solids thus removed to a classification step which includes the removal of oversize by raking same upwardly along a sloping surface, and returning undersize solids from the classification step to the hydroseparation I step.

6. A method for the continuous classification of fine solids suspended in liquid which comprises continuous y removing a portion of the undersize solids by hydroseparation, inipelliug the settled solids mechanically toward a discharge; subjecting the settled solids after discharge to a classification step which includes the removal of the oversize by raking same upwardly along a sloping surface, and the continuous return of the undersize from the classification step to the hydroseparation step independently of the feed to the classifying step.

7. A method for the manufacture of whit-' ing which comprises feeding a suspension of ground chalk and water to a hydroseparator, continuously removing a portion of the whiting in the hydroseparator overflow, conveying the solids settling in the hydroseparator, which comprise the grit and the residue of the whiting, to a classifier through a channel occupied exclusively by the underflow from the hydroseparator flowing away from said hydroseparator, separating the residual whiting from the grit in said classifier, and returning such residual whiting to the hydroseparator.

8. A method for the continuous manufacture of whiting which comprises a continuously feeding a suspension of ground chalk and water to a hydroseparator, continuousl removing a portion of the whiting in t e hydroseparator overflow, conveying the solids settling in the hydroseparator,

which comprise the grit and residue of whating, to a mechanical classifier through a channel occupied exclusively by the underfiow from the hydroseparator flowing away from the latter; separating the residual whiting from the grit in said clawifier; returning the residual whiting with the classifier overflow to the hydroseparator, and removing the grit from the classifier as a separate product.

In testimony whereof, I have signed my name to this specification.

PHILIP 1m McHUGH. 

